noun
unusually large tree; big old tree
Kantō dialect term for a notably large or impressive tree, often of an unclear species. Sometimes used as a placeholder name for a mysterious big tree.
村の入り口に、なんじゃもんじゃと呼ばれる大きな木がある。
At the entrance of the village, there is a big tree called 'nanjamonja'.
このなんじゃもんじゃは樹齢何百年だろう。
I wonder how many centuries old this huge tree is.
Standard Japanese for 'large tree', while なんじゃもんじゃ is a dialectal, colloquial term with a nuance of mystery or impressiveness.
The origin is uncertain. It likely derives from a Kantō dialect expression of surprise or wonder at a large tree, possibly from 何じゃ (what is it?) reduplicated.